Control system for railway car classification yard



Sept. 18, 1962 N. A. BOLTON 3,054,891

CONTROL SYSTEM FOR RAILWAY CAR CLASSIFICATION YARD Filed May 1a, 1956 2 Sheets-Sheet 1 FIG. I.

HUMP f RETARDER CLASSIFICATION IO TRACKS OF YARD FIG. 3.

HUMP LEAVING SPEED r -STORAGE AND TRANSFER CIRCUITS 1 I I I I 8 (B+) (B+) I :{44 50 i CUT LENGTH REF ENTERING DETE T R 5 C 3 52 I SPEED VOLTAGE MomF g MODIFIIEIB FOR A 4 FOR B RETARDER 45 RETARDER 4 REF. ENTERING 2 I SPEED VOLTAGE I E E I REDUCTION REDUCT|ON GEAR'NG GEARING 0.0. MOTOR MOTOR 25 INVENTOR. NABOLTON HIS ATTORNEY Sept. 18, 1962 N. A. BOLTON CONTROL SYSTEM FOR RAILWAY CAR CLASSIFICATION YARD Filed May 18, 1956 2 Sheets-Sheet 2 CLASSIFICATION [TRACKS I 2 SPEED MEASURING MEANS (TRACKS I AND 2) w R. mT ML O mB a A R N O m a Y C B D 4 7 8 k 3 3r 9 3 IIF II A H H H 6 4 D m G W G m 3 G N N A NS WSA DIS D|N5 N? R N 3 E R E R U U EU S 5 S PSE P K AM SAMC SAMC M E A E A M R M R M R T U ns ATTORNEY niteri States atent fifice Patented Sept. 18, 1962 3,054,891 CBNTRGL SYSTEM FOR RAILWAY CAR CLAESIFICATEUN YARD Norman A. Bolton, Rochester, N.Y., assignor to General Railway Signai Company, Rochester, N35. Filed May 18, 1956, Ser. No. 585,734 ll Claim. (M. 246-182) This invention relates to a railway car classification yard, and more particularly pertains to an organization for controlling the speeds of railway cars in accordance with the performance of preceding cars travelling to their respective classification tracks.

In a classification yard, a train of railway freight cars is pushed over the crest of the hump, and each car is then allowed to roll by gravity down the hump and over a number of route-selecting switches to a particular one of a number of destination tracks. In this way, the cars of a train can be classified according to their intended destinations.

The grade of the hump is made suflicient so that the car with the hardest rolling characteristics can travel over track providing relatively high rolling resistance and yet reach a remote destination in the classification yard, despite other adverse factors such as strong headwinds, with suflicient speed to couple onto other cars already in that destination track. Easier rolling cars must, consequently, be decelerated so that they too may reach their destination tracks with a suitable coupling speed. This deceleration is accomplished by providing car retarders along the track rails whose brake shoe beams apply controllable braking pressure to the rims of the car wheels.

In rolling from the crest of the hump, the cars are switched by an automatic switching system from the main track to a plurality of branch tracks and then over additional switches to their final destination tracks. One or more car retarders are located along the main track, and these are called hump retarders. Additional car retarders are included in some of the branch tracks as well so that the speed of each car or out can be controlled for the particular conditions relating to the group of tracks it will travel over, and these retarders are called group retarders.

In modern classification yards, apparatus is provided for automatically controlling the various retarders with the objective of causing each car to reach its intended destination with a preselected coupling speed. The control system determines the cars weight, its rolling characteristics, destination, and various other factors, and from this data determines the desired releasing speed for each car from the group retarder. Speed measuring apparatus is also provided that is effective to release each retarder as soon as it has reduced the car speed to the desired value.

To compute for each car the release speed it should have from the group retarder in order that it will arrive at its destination track with the proper coupling speed, rolla bility conditions must be taken into account, along with the route the car must traverse to reach its classification track. Frequently, however, the actual conditions are found to vary considerably from the assumed values with the result that a car may reach its classification track with a speed considerably above or below the desired value. The change in conditions may be brought about in various Ways, such as by a rainstorm which abruptly decreases the frictional effect of the rails upon the wheels of moving cars. On the other hand, it has been found that after a rainstorm, a coating of rust quickly appears upon the track rails and markedly increases the frictional effect for a time until a number of cars have passed over the track and removed the rust film.

The system of the present invention has been organized to overcome these deleterious effects. Briefly, this is accomplished by measuring the speed of each car as it enters its classification track. It is believed to be sufiicient in practice merely to determine whether car speed is within the normal range of values or is above or below this normal range of values. For each car detected as entering its classification track with a speed above the normal range of speeds, the speeds of following cars leaving the particular group retarder associated with that classification track are decreased by a small amount. For each car detected as entering its classification track with a speed less than the normal speed range, the speed of following cars leaving that group retarder is increased slightly.

The system may thus be considered as providing an integrating feedback organization. An occasional car can be expected to reach its classification track with a speed outside of the normal range but since the cars which deviate thus from the norm can be expected to deviate at random with as many having speeds above as below the normal range, the integrating effect results in substantially no change of release speed from the group retarder. However, upon any change in general conditions, such that many cars tend to arrive at the classification track with a speed below normal and only a very occasional car or none at all arriving at speeds above the predetermined range, then the overall effect is to increase the release speed from the group retarder. Under these circum stances, successive increments of release speed from the group retarder can be expected until normal conditions have been restored, i.e. with most of the cars arriving with speeds in the normal range and with the occasional deviations from the normal range occurring substantially in equal numbers above and below the normal range.

More specifically, the system provides a timing track circuit at the entrance of each classification track. Two timing relays are associated with this track circuit. For a car travelling at a lower speed, neither of the relays will be range of speeds, one of the two timing relays will be actuated but not the other in the interval required for each car or cut of cars to traverse the timing track circuit. For a car travelling at a lower speed, neither of the relays will be actuated as it traverses the timing track circuit, but for a fast car, both timing relays will be actuated in this interval. The timing relays are effective to selectively energize a direct current motor for a brief interval as each car leaves the timing track circuit. For cars having speeds within the predetermined range, the motor is not not. energized. For cars travelling with speeds above the predetermined range, the motor receives one polarity of energization causing it to drive in one direction, while a car travelling with a speed below the predetermined range will cause the opposite polarity of energization to be applied to the motor causing it to drive in the opposite direction. The motor drives, through a reduction gear train, a potentiometer and thus affects the amplitude of a reference voltage provided for a computing circuit organization known as a modifier. The result of a change in this reference voltage is a change in the release speeds of cars from the associated group retarder with the release speed increasing as the reference voltage is increased and vice versa.

Thus, an object of this invention is to provide a control system for a railway car classification yard operating as an integrating feedback organization whereby the speeds of cars are controlled in accordance with the integrated performance of previous cars passing through the classification yard.

Another object of this invention is to provide a car retarder control system wherein a deviation in car speed entering a classification track is effective to modify release speeds from the car retarders in a direction to correct for the deviation.

An additional object of this invention is to provide a control system for a railway car classification yard wherein the speed of each car entering a classification track is determined as falling with, above, or below a normal range of speed values and with the deviations from the normal range being provided as a feedback to correct the group retarder releasing speed to overcome such deviations.

Other objects, purposes, and characteristic features of this invention will in part be obvious from the accompanying drawings, and in part pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to the accompanying drawings in which like reference characters designate corresponding parts in the several views and in which:

FIG. 1 diagrammatically illustrates a portion of the track layout of a typical classification yard;

FIG. 2 illustrates the circuit organization whereby a direct current motor may be selectively operated in accordance with detected deviations in car speed from the normal at the entrance to each classification track; and

FIG. 3 illustrates how the selective control of a motor in accordance with car speed at entrance to the classification tracks may be effective to modify releasing speeds from the group retarders.

To simplify the illustration and facilitate in the explanation of this invention, various parts and circuits constituting the embodiment of this invention are shown diagrammatically and certain conventional illustrations are used. The drawings have been made to make it easy to understand the principles and manner of operation rather than to illustrate the specific construction and arrangement of parts that would be used in practice. The various relays and their contacts are shown in a conventional manner and symbols are used to indicate connections to the terminals of batteries or other sources of electric current.

FIG. 1 illustrates a portion of the track layout in a typical car classification yard. A train of cars is pushed up the hump, and then the cars are allowed to roll singly or in cuts of several cars over the various switches and branching tracks to their final destination tracks. A hump retarder is located ahead of the first switch, and additional retardation is provided by one or more group retarders located in each of the several branching tracks. The gradient of the yard is also shown in FIG. 1 to illustrate that the cars roll by gravity from the hump crest to their intended destination tracks. Only two groups, each including eight classification tracks, are shown, each group being associated with a respective group retarder such as the retarders A and B.

FIG. 2 shows the manner in which the measurement of car speed at the entrance to each classification track of a group is effective to provide a feedback type of input to a DC. motor. This motor operates a variable potentiometer in such a manner that the leaving speed of cars from the associated group retarded is affected. Means similar to that shown in FIG. 2 is provided for each group of classification track to control the associated retarder.

Only two of the classification tracks of a group are shown in FIG. 2, and only the speed measuring means associated with these two tracks is shown in detail. Similar speed measuring means is provided for each of the remaining pairs of tracks of a group as represented by the blocks 11, 12, and 13.

A track circuit is associated with the track switch over which cars must pass to reach either classification tracks 1 or 2. This track circuit includes the track relay ST which is normally energized but becomes dropped away when a car is occupying the track circuit anywhere be tween the insulated joints establishing the limits of this track circuit. Additional track circuits respectively including the track relays TRl and TRZ are provided for each of the classification tracks, and these extend from the limits of the switch track circuit a predetermined distance.

When no cars are occupying any of these circuits, the track relays ST, TR2, and TRI are all picked up so that their back contacts 14, 15, and 16, respectively, are all open with the result that no energy can be applied to the two timing relays T1 and T2 which are provided with slow release characteristics as indicated by the heavy base line of the symbol representing each relay. However, as soon as a car enters the switch track circuit so that relay ST drops away, the closure of back contact 14 of this relay establishes a circuit to energize both the timing relays T1 and T2.

Assuming that the car is routed to classification track No. l, as soon as its front truck enters the timing track circuit so that track relay TRl drops away, a circuit is established through front contact 17 of relay TRZ, and back contact 18 of relay TRl, and the winding of relay STK so that this relay is picked up. At this time, the closed back contact 16 of relay TRl places the (-1-) energy on wire 19 but the now open back contact 20 of relay STK prevents the energization of the timing relays T1 and T2 through this circuit although these relays are both still energized through back contact 14 of relay ST.

When the car advances so that it is fully within the timing track circuit, and with the rear truck of the car removed from the switch track circuit, relay ST is restored to its normal picked-up condition. The opening of back contact 14 of this relay then deenergizes both the timing relays T1 and T2. The drop-away time of relay T1 is adjusted relative to the length of the timing track circuit and to the speed of a car so that a car travelling with a speed falling within the normal range of speeds for a car at this point will traverse the timing track circuit in a time somewhat longer than that required for relay T1 to drop away. A car travelling with a speed above the normal range will traverse the timing track circuit in a time less than that required for relay T1 to drop away. On the other hand, the dropping away time of relay T2 is adjusted so that it will drop away only when a car takes more than the normal length of time to traverse the timing track circuit indicating that such car is travelling at a speed below the normal range of speeds. Therefore, at the instant a car leaves the timing track circuit, the conditions of the two timing relays T1 and T2 together determine the speed range of the car. That is, if at that moment, relay T1 is dropped away but relay T2 has not yet dropped away, it is then established that the car travelled over the timing track circuit in the normal time and thus was travelling at a speed falling within the normal range of speeds. If both relays T1 and T2 are dropped away at that moment, it indicates that the car took a more than normal length of time to travel over the track circuit, thereby giving relay T2 as well as relay T1 an opportunity to drop away. This indicates that such a car was travelling at a speed falling below the normal speed range. The third condition is represented by both relays T1 and T2 being picked up at the moment the car leaves the timing track circuit. This condition indicates that the car passed through the timing circuit so quickly that not even relay T1 had an opportunity to drop away, and this indicates that the car was travelling at a speed above the normal speed range.

It is desired that the conditions of the two timing relays T1 and T2 be maintained for a brief interval following the exit of the car from the timing track circuit in order that the proper input can be applied to the DC. motor. Thus, it is necessary that the pick-up circuits for these two relays not be immediately re-establi-shed since this would immediately pick up either or both of the timing relays in the event that they had dropped away during the time the car was passing through the timing track circuit. On the other hand, it is also required that either or both of these relays which had not had sufficient time to drop away during the interval the car was traversing the timing track circuit also not be allowed to drop away during this brief interval occurring when the car first leaves the timing track circuit.

These conditions are met by controlling the separate stick circuits of the timing relays T1 and T2 through contact 21 of the relay STK. As already explained, relay STK is picked up while the car is in the timing track circuit. As soon as the car leaves the timing track circuit so that both relays TRZ and TRl are picked up, the pick-up circuit for relay STK is immediately interrupted. Relay STK does not immediately drop away, however, because of its slow release characteristics as indicated by the heavy base line for the symbol representing the relay. As a result, energy is supplied from (-1-), through front contact 17 of relay TR2, front contact 18 of relay TR1, and front contact 21 of relay STK, to wire 22. If either or both of the relays T1 and T2 is then picked up, a stick circuit is completed through its respective front contact 23 or 24 and the lower winding of the respective relay to maintain it momentarily energized. At this time also, the picked-up conditions of the track relays ST, TR2, and TRl prevent the energization of the upper winding of either relay T1 or T2. Both these timing relays are thus maintained in the condition they had at the instant the timing track circuit was vacated by the car. It is not until the relay STK has dropped away that the stick circuit described is opened at front contact 21 so that both timing relays can then be dropped away.

It is in the brief interval following the vacating of the track circuit resulting in the deenergization of relay STK but before this relay has had time to release that the DC. motor 25 receives its momentary input. Thus, a circuit is established which supplies energy through front contact 26 of relay TR2, front contact 27 of relay TR1, and front contact 28 of relay STK, to wire 29. If the car was travelling with a speed falling within the normal speed range so that relay T1 is dropped away but relay T2 is still picked up, then obviously no circuit can be completed from the now energized wire 29 to either wire 30 or wire 31. Neither of the relays S nor F, therefore, is picked up. On the other hand, for a car travelling at a speed above the normal speed range so that both relays T1 and T2 are picked up, the energy on wire 29 can then be applied through front contact 32 of relay T1, front contact 33 of relay T2, to wire 31, and then through back contact 34 of relay S and the winding of relay F to However, for a car travelling with a speed below the normal speed range so that both relays T1 and T2 are dropped away, a similar circuit is provided through back contact 32 and 35 of relays T1 and T2, respectively, wire 30, the winding of relay S and back contact 36 of relay F to energize the winding of relay S. This energization of either relay S or F is maintained only until relay STK drops away and opens its front contact 28. The result is then that neither of the relays S nor F is energized for a car travelling at the normal speed; for fast cars, the relay F is picked up, and for slow cars the relay S is picked up.

If relay S is picked up, a circuit is completed to energize the DC. motor which includes the front contacts 37 and 38 of this relay S, and this circuit results in a flow of current from left to right through the motor. Conversely, the picking up of relay F establishes a circuit through its front contacts 39 and 40 that produces a flow of current from right to left through the motor. This circuit organization thus provides that the motor will rotate momentarily in one direction for fast travelling cars and in the opposite direction for the same length of time for slow travelling cars, but will not be energized at all for cars travelling at a speed falling within the predetermined range of speeds.

Similar speed measuring means is provided for each pair of classification tracks. Thus, a car routed for either track 3 or track 4 will cause the speed measuring means 11 to selectively actuate the relays S and F for a car travelling below or above the preselected speed range respectively. The inclusion of contact '34 in the pick-up circuit of relay F and the similar inclusion of contact 36 in the pick-up circuit of realy S prevents the simultaneous picking up of both of these relays. It thus becomes impossible for both of the relays S and -F to be simultaneously picked up in response to different inputs from different speed measuring means.

FIG. 3 illustrates the manner in which the DC. motor 25 of FIG. 2 is effective through a reduction gearing 41 to drive the movable tap 42 of a potentiometer 43. This potentiometer 43 is included in a series of potentiometers connected in series between (-1-) and ground. The movable taps on the two potentiometers 44 and 45 are connected to the top and bottom terminals, respectively, of a resistor 46 having a number of fixed taps. As is fully disclosed in the co-pending application of J. H. Auer, Jr., Ser. No. 578,047, filed April 13, 1956, the hump leaving speed storage and transfer circuits 47 are selectively controlled -in accordance with the speed at which each car leaves the hump retarder. The effect is diagrammatically illustrated by a rotary contact 48 which is capable of moving to any one of a number of fixed positions entirely in accordance with the speed at which a car leaves the hump retarder. The voltage that then appears on wire 49 is a function of the position of the rotary contact and is thus dependent upon the speed of the car as it left the hump retarder.

As indicated in FIG. 3, this voltage upon wire 49 is the reference entering speed voltage that is applied to the modifier associated with the A group retarder. This reference entering speed voltage is a DC. voltage whose level is proportional to the expected speed of a car of known rolling characteristics at the entrance to the group retarder. This expected speed is, of course, dependent upon the speed at which the car left the hump retarder, and it is for this reason that the hump leaving speed storage and transfer circuits 47 are provided so that they can be effective to set the level of this reference entering speed voltage in accordance with the hump leaving speed.

As is disclosed in the previously mentioned application of J. H. Auer, Jr., Ser. No. 578,047, filed April 13, 1956, the speed of each car is again measured as it approaches the group retarder and this actual speed is compared with the expected speed, and the difference in these two speeds then establishes the rolling characteristics of the car. This quantity is then used as a factor in determining the desired release speed of each car from the group retarder. It follows from this description, that the speed at which a car leaves the group retarder can be affected by changing the reference entering speed Voltage. Thus, an increase in this reference entering speed voltage tends to increase the leaving speed from the group retarder.

The cut length detector 50 is effective in this way to act on the value of the reference entering speed voltage. Cuts of several cars cannot roll freely between hump and group retarders for as long a time as can an individual car. Such a cut therefore arrives at the group retarder at a lower speed than would a single car having substantially the same rolling characteristics. As a result, the cut length detector 50 is provided to arbitrarily decrease the reference entering speed voltage for cuts in excess of one or two cars. More specifically, the detection of a cut of several cars in length causes the cut length detector 50 to close back contacts 51 and 52. This places a shunt between the tap on potentiometer 53 and the lower terminal of the potentiometer, thereby decreasing the resistance in the lower portion of this series of potentiometers. The result is decrease in voltage between the two taps on the potentiometers 44 and 45, thereby decreasing the reference entering voltage appearing on wire 49. The closure of back contact 52 similarly decreases the reference voltage applied to the modifier for the B group retarder.

In the same way, movement of the tap of potentiometer 43 by the DC. motor 25 is effective to raise or lower the voltage existing on the taps of the two potentiometers 44 and 45 and thus on wire 49 also. When the tap is moved upward towards the upper terminal of the potentiometer 43, the efiective resistance provided by the potentiometer is increased With a resulting increase of reference entering voltage on wire 49. Similarly, moving the tap lower on this potentiometer 43 results in a decrease in reference entering speed voltage.

Each input that the DC. motor receives in response to a single car results in only a very small movement of the tap 42 on potentiometer 43 and a correspondingly small voltage change of the reference entering speed voltage. It is only when cars are consistently entering their classification tracks of a particular group of such tracks with a speed above or below the normal speed range that the reference entering speed voltage is appreciably affected. The result of such change in the reference entering speed voltage tends to correct the deviations so that the DC. motor 25 then receives less inputs tending to drive it in that direction. If car speeds deviate from the normal in the opposite direction, then the DC. motor receives inputs of the opposite polarity tending to drive the potentiometer tap in the opposite direction with the result that the reference entering speed voltage then also varies in the opposite direction. The system is thus self-correcting and tends to maintain the speeds of cars at the entrance to theclassification tracks within the predetermined range of such speed.

The preferred embodiment disclosed herein comprises a single D.C. motor and potentiometer for each group of classification tracks and with the resulting control being exercised only upon the control apparatus for the particular retarder associated with that group of classification tracks. The principles of this invention apply equally well, however, if all that various speed measuring means associated with the various tracks provide inputs to a single motor which then controls individual potentiometers each relating to a respective control means for a group retarder. Furthermore, although this system has been particularly disclosed with reference to a gravity type classification yard having a plurality of car retarders, it is apparent that the principles disclosed and claimed herein apply as well to yards which are flat and wherein the cars are moved to their classification tracks by other means such as car accelerators.

What I claim is:

A speed measuring system for the control of a group car retarder disposed in a group track from which cars pass through a track switch selectively to either of two laterally disposed classification tracks comprising:

(a) a detector track circuit for said track switch including a track relay for registering the presence of a car,

([2) a track circuit including a track relay in each of the classification tracks adjoining said detector track circuit for registering the passage of a car along a pre-determined distance of trackway,

(0) two normally inactive timers operable when initiated to time different time intervals,

(d) circuit means including said track relay of said detector track circuit and said track relay of either one of said adjoining track circuits responsive to the passage of a car from the detector track circuit to an adjoining track circuit for initiating both of said timers simultaneously, and

(e) circuit means responsive to the passage of a car out of either of said adjoining track circuits for selectively registering any one of at least two speed classifications in accordance with the condition of said timers at that time.

References Cited in the file of this patent UNITED STATES PATENTS 1,586,989 Haines June 1, 1926 1,720,635 Preston July 9, 1929 2,045,201 Rabourdin June 23, 1936 2,076,955 Livingston Apr. 13, 1937 2,669,489 Kuhn Feb. 16, 1954 2,770,775 Agnew Nov. 13, 1956 2,814,996 Albrighton Dec. 3, 1957 FOREIGN PATENTS 208,415 Australia Oct. 27', 1955 OTHER REFERENCES Ser. No. 320,937, Rabourdin (A.P.C.)', published May 25, 1943, now abandoned. 

